Use the more portable shebang `/usr/bin/env bash`

Not all distros have bash in `/bin/bash`. In fact, most distros are
moving binaries away from `/bin` and into `/usr/bin` (even debian!). But
still, not all distros have bash in `/bin` or `/usr/bin`. However,
pretty much all of them have `env` in `/usr/bin`. `/usr/bin/env bash`
searches `$PATH` for the bash executable, and is the most portable
shebang to use.

autopostgresqlbackup

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # {{{ License and Copyright
 # PostgreSQL Backup Script